Case Study of Mechanical Performance of Kilometer Level Cable-Stayed Bridges with Steel-Concrete Composite Deck

In view of the shortcomings of large dead-weight and limited spanning capacity for traditional composite girders and the fatigue failure and pavement deteriorations for steel girders, composite girders with lightweight composite deck emerged as good alternatives. Thus, trial design schemes of long-span cable-stayed bridges with steel-NC (normal concrete) and steel-UHPC (ultra-high performance concrete) composite decks were proposed under different span conditions. The static performance and technical feasibility of the designed bridges and the influence of structural parameters of main girder on different static effects were analysed, based on which, the determinative static effects and their variation with span length were investigated. The results show that the designed NC-slab schemes with main spans no more than 900 m can meet the requirements of static strength, stiffness and stability, while the 1000 m NC-slab scheme cannot meet the compressive strength requirements of the concrete slab. The UHPC-slab schemes meet the static requirements even when the main span reaches 1100 m, and the most unfavourable static effect turns to be the maximum compressive stress of steel girders. The main structural parameters of the main girder that most affect the unfavourable static effects include the main girder height and the thickness of the lower flange steel plate. Using UHPC-slab instead of NC-slab improves the spanning capacity of cable-stayed bridges by approximately 25%, close to the reduction rate of the dead-weight of main girder.